JPH0455107A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To restrain the occurrence of a rut wandering phenomenon while excellent high speed, wear-resistance and low fuel cost performance are kept by providing saw-toothed projecting and recess portions in the peripheral direction of a tire on both edges of a tread surface, disposing a striation adjacent thereto and further disposing sipes. CONSTITUTION:A reinforcing belt 2 comprises four layers and is formed by a metal cord. Plural main grooves 4 are provided on a tread surface 10, and saw-toothed projecting and recess portions 5 are formed in the peripheral direction on both edges thereof. The projecting and recess portions 5 are formed by continuously providing V-shaped grooves 8. Further, a striation 12 is disposed adjacent to the projecting and recess portions 5 and sipes 14 reaching the striation 12 are disposed in recess portions of the projecting and recess portions 5. When the projecting and recess portions 5 come into contact with the wall surface of a rut, the tip 9 is brought into point contact therewith, and the contact is performed in such a manner as to increase the reaction force gradually. As the contact pressure is increased, block 15 outside the striation 12 fall down to the striation 12 side. As the repulsive force is small, a tire will not be pushed back from the wall surface of the rut, but can get over the rut easily. Further, the biting performance of the tire to the wall surface of the rut can be improved by the projecting and recess portions 5 so as to promote the escape from the rut.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire suitable for use in heavy-duty vehicles such as trucks and buses.

[Conventional technology]

In recent years, pneumatic radial tires have come to be used in heavy-duty vehicles such as trunks and buses, demonstrating their excellent high speed, wear resistance, and fuel efficiency. In this pneumatic radial tire for heavy-duty vehicles, the reinforcing belt layer of the tread portion is generally made of metal cord in order to withstand the heavy load, and has extremely high rigidity.

However, these heavy-duty pneumatic radial tires with high tread rigidity are used with even higher internal pressure, so when they are driven on a rutted road surface, they release excessive pressure from the road surface when escaping from the ruts. A so-called wandering phenomenon occurs in which the handle is taken off by an external force.

[Problem to be solved by the invention]

The present invention was made to eliminate such conventional drawbacks, and its purpose is to maintain the excellent high speed, wear resistance, fuel efficiency, etc. of heavy-duty pneumatic radial tires. To provide a pneumatic radial tire for heavy loads that is less likely to cause rut wandering.

[Failure to solve the problem]

That is, the pneumatic radial tire for heavy loads of the present invention is a pneumatic radial tire for heavy loads in which a reinforcing belt made of metal cord is arranged in the trend part and a plurality of main grooves extending in the circumferential direction of the tire are provided in the trend tread. , a sawtooth-like uneven portion is provided along the tire circumferential direction on both edges of the tread surface, and a narrow groove extending in the tire circumferential direction is arranged on the inner side of the tire adjacent to the uneven portion, and a recessed portion of the uneven portion is provided. The invention is characterized in that a sipe is provided extending from the groove to the narrow groove.

1 to 3 illustrate a heavy-duty pneumatic radial tire according to an embodiment of the present invention, in which 1 is a trend section, 2 is a reinforcing belt disposed in the circumferential direction of the tread section 1, and 3 is a pneumatic tire for heavy loads according to an embodiment of the present invention. is a carcass. The carcass 3 is composed of a small number of layers (in this embodiment The reinforcing belts 2 are composed of four layers (4 layers) and are mainly composed of metal cords.These reinforcing belts 2 form an angle of 15 to 30 degrees with respect to the circumferential direction of the tire, and the layers intersect with each other.

On the other hand, the contact surface of the tread portion 1, that is, the tread surface 10
A plurality of main grooves 4 extending in the circumferential direction of the tire are provided, forming a rib pattern. This tread surface 1
Sawtooth-like uneven portions 5 are provided on both edges of the tire 0 along the circumferential direction of the tire. The uneven portion 5 is formed by continuously providing a groove 8 shaped like a 7 in the shoulder portion 6 of the tread surface 10 in the tire circumferential direction from the trend tread surface 10 to the shoulder portion 7 and facing in the direction of the rotational axis of the tire. has been done.

Further, near both edges of the tread surface 10, the uneven portions 5
A narrow groove 12 extending in the tire circumferential direction on the inner side of the tire adjacent to
are arranged respectively.

Further, the uneven portions 5 are provided on both edges of the tread surface 10.
A sipe 14 reaching the narrow groove 12 is disposed in the recess. This sipe 14 allows the outer rib 13 of the narrow groove 12 to
are separated in the radial direction of the tire so as to substantially form blocks 15. The direction of the sipes 14 may be in the width direction of the tire (although it is not necessarily limited to the direction of the tire rotation axis as in the embodiment shown in the figure, but may be in an oblique direction).

In this way, sawtooth-like uneven portions 5 are provided along the tire circumferential direction on both edges of the tread surface 10, and narrow grooves 12 extending in the tire circumferential direction are provided on the inner side of the tire adjacent to the uneven portions 5, and By arranging the sipes 14 in the recesses of the uneven portion 5, the rigidity of both edges of the trend tread surface 10 can be reduced without substantially reducing the contact area of the tread surface 10.

In the trend tread 10 having such a configuration, when the uneven portion 5 comes into contact with the wall surface of the rut, the tip 9 of the uneven portion 5 comes into point contact with the wall surface of the rut, and the reaction force is very small at first, but gradually the reaction occurs. Make contact in such a way that the force increases. Moreover, the contact pressure increases (as the contact pressure increases, the blocks 1 outside the narrow groove 12
5 comes to fall down toward the narrow groove 12 side. In such a case, even if the blocks 15 are incompressible, their repulsive force is small, so the tire will not be pushed back from the wall of the rut by the reaction force of the blocks 15, and the tire will not be able to easily get over the rut. can. Moreover, having sawtooth-like uneven portions 5 on both edges of the tread surface 5 improves the ability of the tire to bite into the wall surface of the ruts, thereby facilitating escape from the ruts.

When the pitch of the uneven portions 5 described above is l, and the width of the uneven portions 5 in the tire rotation axis direction is a, a/β is preferably within the range expressed by the following formula.

That is, Q, l<a/A<0.2 If a/β is within the above range, the rigidity of both edges of the tread surface can be reduced without substantially reducing the tire contact area. This makes it difficult for the rut wandering phenomenon to occur. Further, the depth hl of the uneven portion 5 is preferably greater than or equal to the width a of the uneven portion 5 in the tire rotation axis direction and equal to or less than the depth H of the main groove 4 (a<hl≦H).

On the other hand, the distance d1 from the shoulder 6 of the tread surface 10 to the outer edge of the narrow groove 12 is at least the width a of the uneven portion 5 in the tire rotational axis direction, and is 1/40 of the ground contact width TW of the tread surface 10.
A range of 1/10 to 1/10 is preferable. Also, the depth h of the narrow groove 12
2 is preferably equal to the depth H of the main groove 4 in order to maintain wandering prevention performance, and more preferably within the range of O,'71 (<hz<1.0H). In general, a size of about 15 squares is suitable.The groove width of the narrow groove 12 is preferably in the range of 1 to 5 fl, more preferably about 2 to 3 fl.

Furthermore, the depth of the sipe 14 is equal to the depth hl of the uneven portion 5 on both edge sides of the tread, and the depth h of the narrow groove 12 on the narrow groove side.
It is preferable to make it equal to 2.

〔Example〕

The present invention tire having the structure shown in FIGS. 1 and 2 and the conventional tire having the tread surface shown in FIG. A test in which the vehicle was equipped with an empty vehicle and drove on a rutted test course at a speed of 80 to 90 km/h while driving straight in the ruts, entering and exiting the ruts, and intentionally hitting the tires against the rut walls. was conducted with 10 test drivers.

The feeling of each test driver at that time was scored using a 10-point system based on the conventional tire, and the average value of the 10 drivers was expressed as the wandering prevention performance.

The above feeling score includes the frequency of wandering, the amount of wandering movement, the speed of wandering movement,
We evaluated the convergence of wandering, steering wheel response, and the vehicle's behavior in and out of ruts, and the evaluation results are shown in the table.

Note that the tire size is 10.0OR2014PR.

From this "table", it can be seen that the tire of the present invention has extremely excellent wandering prevention performance.

〔Effect of the invention〕

As described above, the present invention provides a heavy-duty pneumatic radial tire in which a reinforcing belt made of a metal cord is disposed in the trend portion and a plurality of main grooves extending in the circumferential direction of the tread are provided on the tread surface. Sawtooth-like uneven portions are provided on both edges along the tire circumferential direction, and narrow grooves extending in the tire circumferential direction are provided on the inner side of the tire adjacent to the uneven portions, and the narrow grooves are formed from the concave portions of the uneven portions. By providing sipes that extend across the entire length, the rut-wandering phenomenon becomes even more difficult to occur, while maintaining the excellent high speed, wear resistance, and fuel efficiency of heavy-duty pneumatic radial tires. You will be able to drive safely without having your steering wheel stuck in a rut.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of the tread part of a radial tire according to an embodiment of the present invention, FIG. 2 is a plan view of the tread part of the radial tire, and FIG. 3 is a perspective view of the main part of the radial tire. FIG. 4 is a plan view of the tread portion of a conventional pneumatic radial tire. DESCRIPTION OF SYMBOLS 1... Tread part, 2... Reinforcement belt, 4... Main groove, 5... Uneven part, 10... Tread surface, 12...
...Narrow groove, 14...Sipe.

Claims (1)

[Claims] In a heavy-duty pneumatic radial tire in which a reinforcing belt made of metal cord is disposed in the tread portion and a plurality of main grooves extending in the circumferential direction of the tire are provided on the tread surface, grooves are provided on both edges of the tread surface along the circumferential direction of the tire. A tire for heavy loads, which is provided with a serrated uneven part, a narrow groove extending in the circumferential direction of the tire on the inner side of the tire adjacent to the uneven part, and a sipe extending from the concave part of the uneven part to the narrow groove. Pneumatic radial tire.